let watermark = {}

let setWatermark = (str, time, boxId, timer) => {
  let id = '1.23452384164.123412416';
  let box = document.getElementById(boxId)
  if (!box) {
    clearInterval(timer)
    return
  }
  if (document.getElementById(id) !== null && box.contains(document.getElementById(id)) ) {
    box.removeChild(document.getElementById(id));
  }

  //创建一个画布
  let can = document.createElement('canvas');
  //设置画布的长宽
  can.width = 250;
  can.height = 150;

  let cans = can.getContext('2d');

  //旋转角度
  cans.rotate(-20 * Math.PI / 180);
  cans.font = '16px Microsoft JhengHe';
  //设置填充绘画的颜色、渐变或者模式
  cans.fillStyle = 'rgba(200, 200, 200, 0.40)';
  //设置文本内容的当前对齐方式
  cans.textAlign = 'left';
  //设置在绘制文本时使用的当前文本基线
  cans.textBaseline = 'Middle';
  //在画布上绘制填色的文本（输出的文本，开始绘制文本的X坐标位置，开始绘制文本的Y坐标位置）
  cans.fillText(str, can.width / 3, can.height / 2);
  cans.fillText(time, can.width / 3, 130);

  let div = document.createElement('div');
  div.id = id;
  div.style.pointerEvents = 'none';
  div.style.top = '0';
  div.style.left = '0';
  div.style.position = 'absolute';
  div.style.zIndex = '200';
  div.style.width = '100%';
  div.style.height = '100%';
  div.style.background = 'url(' + can.toDataURL('image/png') + ') left top repeat';
  box.appendChild(div);
  return id;
}

// 该方法只允许调用一次
watermark.set = (str, time, boxId) => {
  let id = setWatermark(str, time, boxId);
  let timer = setInterval(() => {
    if (document.getElementById(id) === null) {
      id = setWatermark(str, time, boxId, timer);
    }
  }, 500);
  window.onresize = () => {
    setWatermark(str, time, boxId, timer);
  };
}

export default watermark;